In systems incorporating rotating drive shafts, it is often necessary to know the torque and speed of such shafts in order to control the same or other devices associated with the rotatable shafts. Accordingly, it is desirable to sense and measure the torque in an accurate, reliable, and inexpensive manner.
Sensors to measure the torque imposed on rotating shafts, such as but not limited to shafts in automotive vehicles, are utilized in many applications. For example, it might be desirable to measure the torque on rotating shafts in a vehicle's transmission, or in a vehicle's engine (e.g., the crankshaft), or in a vehicle's automatic braking system (ABS) for a variety of purposes known in the art.
One application of this type of torque measurement is in electric power steering systems wherein an electric motor is driven in response to the operation and/or manipulation of a vehicle steering wheel. The system then interprets the amount of torque or rotation applied to the steering wheel and its attached shaft in order to translate the information into an appropriate command for an operating means of the steerable wheels of the vehicle.
Prior methods for obtaining torque measurement in such systems have been accomplished through the use of contact-type sensors directly attached to the shaft being rotated. For example, one such type of sensor is a “strain gauge” type torque detection apparatus, in which one or more strain gauges are directly attached to the outer peripheral surface of the shaft and the applied torque is measured by detecting a change in resistance, which is caused by applied strain and is measured by a bridge circuit or other well-known means.
Another type of sensor used is a non-contact torque sensor wherein magnetorestrictive materials are disposed on rotating shafts and sensors are positioned to detect the presence of an external flux which is the result of a torque being applied to the magnetorestrictive material.
One area where torque sensing is important is in the area of automatic transmission systems. One example of an automatic transmission is disclosed in U.S. Pat. No. 6,887,178, entitled “Automatic Transmission” which issued to Miyazaki, et al. on May 3, 2005. U.S. Pat. No. 6,887,178 is incorporated herein by reference in its entirety. Another example of an automatic transmission is disclosed in U.S. Pat. No. 6,892,533, entitled “Automatic Transmission” which issued to James C. Beattie on May 17, 2005. U.S. Pat. No. 6,892,533 is incorporated herein by reference in its entirety. A further example of an automatic transmission is disclosed in U.S. Pat. No. 6,907,801, entitled “Automatic Transmission” which issued to Hiromichi Shimaguchi on Jun. 21, 2005. U.S. Pat. No. 6,907,801 is also incorporated herein by reference in its entirety.
To date, torque sensors have not been successively implemented in the context of automatic transmission systems. It is believed that if implemented properly, torque sensors have the ability to provide enhanced cam and crank shaft position sensing capabilities. The innovations disclosed herein are believed to provide for an improvement over the lack of torque sensors in automatic transmission systems and automotive engine and components thereof.